91 cougar low oil pressure

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John - 20 Jun 2005 01:31 GMT

Hey all, reader of both groups, hoping someone can help.

I have a 91 cougar XR7 5.0L HO that has recently started showing low oil
pressure on the gauge. Needle used to read straight up-and-down between the
R and the M of NORMAL, now the needle sits at the N or lower. Sometimes it
will go to about the O but that is as high as it ever gets. Most recently
it is a N or lower.
I was running 5W-30 with 1/2 a quart of Marvels, I've since changed the oil
to castrol 10w30 only, still no change. Next stop is a new sending unit. I
tried cleaning the connections but couldn't get to the connection inside the
wire clip, too tight in there.
I know that these electrical gauges can be iffy if the connections aren't
clean, should I be worried? Looks like many in the 'stang NG have seen this
with no real issues.
Engine has 160K on it but runs great, no noises and still a ton of power. I
might occasionally have to add a quart between changes, but not often if at
all.

Any ideas?

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John

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Backyard Mechanic - 20 Jun 2005 01:53 GMT

Generally speaking, dont worry about it.

Changing the sender might be a good idea,... but sometime around the
early nineties Ford stared using "foolers" which is a switch for an idiot
light and a 20 ohm resistor.

If your sender is compact and you can get a socket over it to take it
out, it's a fooler. Esp if the needle went to a certain reading when you
started the car and stayed there, no matter the rpm or how warm engine
is.

I run nothing but Mobil 1 synthetic in my old engines... might add a
quart of regular oil if it's just before my regular 10,000 mile change.

Try 15w-50 or a combo of mobil 1 (what I do if the engines loose) weights
to keep the pressure where you like it.

What oil were you using BEFORE the Castrol?

> Hey all, reader of both groups, hoping someone can help.
>
[quoted text clipped - 15 lines]
>
> Any ideas?

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John - 20 Jun 2005 02:19 GMT

> Generally speaking, dont worry about it.
>
[quoted text clipped - 4 lines]
> If your sender is compact and you can get a socket over it to take it
> out, it's a fooler.

Yup, even thought how easy it would be to change because of that. Do I need
to drain the oil to change this?

Esp if the needle went to a certain reading when you

> started the car and stayed there, no matter the rpm or how warm engine
> is.

Not much change if at all. It may move down a little as the engine gets
hotter since the oil is thinning out, but other times it may go up a tiny
bit, but not much at all. Generally at idle or at 3500 rpms the needle will
not change more than half a letter at most.
However, when I change the oil, it does take a second or two for the needle
to move from dead bottom to the current pressure reading. For this reason I
had thought it was a real sensor.

> I run nothing but Mobil 1 synthetic in my old engines... might add a
> quart of regular oil if it's just before my regular 10,000 mile change.
[quoted text clipped - 3 lines]
>
> What oil were you using BEFORE the Castrol?

It has only had dino oil, Penzoil, Quaker, Valvoline, Motorcraft, always
5w-30.

John

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Backyard Mechanic - 20 Jun 2005 02:53 GMT

"John" <noone@here.com> wrote

> It has only had dino oil, Penzoil, Quaker, Valvoline, Motorcraft,
> always 5w-30.
>
> John

From my personal viewpoint based on facts observed in 60's and carried on
as unreasonable, unsupported bias to this day....Pennzoil and QS are
crap!
- - - - - - - - -

S, then you DO have an idiot gauge.

I suggest finding a way to hook a 12 volt troubleshooting light to the
ender and the other lead to 12volt pos.

If it flickers, while running you have problems... But it MAY be the
sender itself got oil in it, thus a resistance when it's closed
(running).
Otherwise,
Remove the lead from sender and ground it, ign on.. I'm guessing it will
go to where it used to.

If it does... change sender. If it doesnt, problem is in your guage
cluster or the wiring to it (doubt that last though or it would show
erratic.)

If the gauge shows normal, grounded, but changing sender doesnt fix your
problem, then you may indeed have low oil pressure... though needle
should not vary when it is cold.

You MAY also have a bad engine-frame ground though this should affect the
temp gauge, too

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